Thanks for the responses gents.
I with try the cancel AoE as well but if it does not take effect until the script has run might it still not call the convo because an npc is incapacitated.
The issues I have seen are:
1. When a party is in combat, the mage fires off an incendiary cloud and this persists after everyone is dead. For some reason, while the spell is in effect the characters remain in combat mode and the convo does not fire.
2. This is the major issue that has cropped up twice - If the npc that starts the conversation has died then they do not come back to life (as per stock death script) until the spell has completed. Thus the script fires on death but the convo cannot fire and it does not work.
This only seems to be for the IC spell, for vine mine/entangle/black tentacles etc this does not seem to be the case.
I will try KevL suggestions and check the spell 2da to see perhaps if this spell has different settings than the others (that will be an adventure:)
PJ